Method, system and molding tool for manufacturing components from composite fiber materials

ABSTRACT

In a method for manufacturing components from composite fiber materials, at least one placeholder is inserted into a recess in a molding tool, wherein the unfinished component is subsequently produced, the placeholder is removed, at least one lifting pad is inserted into the recess and the unfinished component is removed from the molding tool by inflating the lifting pad. In a system for manufacturing components from composite fiber materials, the component removal process is monitored and controlled by a computer unit in order to prevent predetermined maximum component loads from being exceeded. The gentle component removal process makes it possible to avoid consequential costs for repairing or reworking the components.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 13/140,152, filed on Jun. 16, 2011, which application is a nationalphase entry under 35 U.S.C. §371 of International Application No.PCT/EP2009/065712, filed Nov. 24, 2009, published in German, whichclaims the benefit of the filing date of U.S. Provisional PatentApplication No. 61/201,915, filed Dec. 16, 2008, and of German PatentApplication No. 10 2008 062 477.2 filed Dec. 16, 2008, all of which arehereby incorporated herein by reference.

TECHNICAL FIELD OF INVENTION

The invention pertains to a method for manufacturing components fromcomposite fiber materials, a system for manufacturing components fromcomposite fiber materials, a molding tool for the manufacture ofcomponents from composite fiber materials, a use, as well as an aircraftcomprising components that were manufactured with the method accordingto the invention.

BACKGROUND OF THE INVENTION

In the manufacture of components from fiber-reinforced plastics by meansof molding tools—whether male or female molding tools—it is unlikely forthe component to separate from the molding tools by itself after thehardening process. It is therefore necessary to carry out a manualcomponent removal. The term “component removal” refers to the removal ofthe hardened component from the mold. According to the current state ofthe art, this is realized by lifting the component on the component edgeby means of wedge tools, wherein these wedge tools may consist, forexample, of wood or a soft plastic such as, for example,polytetrafluoroethylene.

With larger components, it is furthermore required to “readjust” thewedge tools before the component completely separates from the mold.Particularly with large-surface shell components, for example, in theform of wings, aircraft fuselage shells, solar panels and the like, thewedge tools needs to be driven very far in the direction of thecomponent center before the component ultimately separates from themold.

If the molding tools are insufficiently or incorrectly coated with areleasing agent and the component has very large dimensions withinferior accessibility, it may be necessary to utilize other mechanicaldevices with a greater leverage effect for separating the component. Themanual use of such mechanical devices may also be required if thecomponent geometry sectionally comprises a slight undercut.

DE 198 54 735 A shows a bushing made of thermally deformable as well asa method for producing the such. The bushing consists of a substantiallypipe-shaped base body with a cylindrical outer circumference with asubstantially constant radius and an inner cylindrical circumferencethat is tapered in axial direction.

DE 756 995 shows a pressing mold for processing curable compressedlaminated material, from which mold the pressed component is removableby means of compressed air.

Molding tools with so-called “sliding inserts” cannot be used forcomponents with high surface requirements such as, e.g., aerodynamicsurfaces or functional surfaces of an aircraft that are subject tostrict tolerances. The reasons for this are, for example, the facts thatthe wedge tools may be outlined on the component surface, that so-called“lugs” may be created in the matrix material and that it is difficult toproduce a seal against resin during the component hardening.

SUMMARY OF THE INVENTION

Accordingly, an aspect of the invention proposes a method formanufacturing components from composite fiber materials that diminishesor entirely eliminates at least a few of the above-describeddisadvantages. An aspect proposes a method of this type, in whichlarge-surface components can also be carefully removed from a moldwithout damaging a component surface, creating projections or generallysubjecting the component to excessive mechanical loads.

According to one important aspect of the method to the invention, acomponent molded by laying and laminating fiber material in a moldingtool and subsequently hardening the component is not removed from themolding tool by means of wedge tools or other tools that significantlyintervene mechanically, but rather with inflatable lifting pads.Accordingly, an aspect of the invention is characterized in that a muchmore controllable removal method is used. Due to the use, for example,of pneumatically controlled lifting pads, the force or the path duringthe removal can be controlled such that a largely careful separation ofthe component from the molding tool is ensured.

In a first concept of a method according to the invention, a moldingtool is used that comprises a recess for a lifting pad on the futurecomponent edge. In order to preserve the surface, a placeholder isinserted into this recess before laying and laminating the component inthe molding tool, wherein said placeholder completely fills out therecess and ends flush with the surface of the molding tool. In thiscase, the placeholder may consist of one part or be realized in the formof a multipart laminate.

Depending on the surface requirements of the component, the recessshould lie in a region outside the actual component, namely in aso-called “trimming region.” The component to be manufactured extendsinto this trimming region that lies outside the desired final shape.After hardening and removing the component from the molding tool, thecomponent can be trimmed to its final shape within the trimming region.This is particularly sensible because it cannot be guaranteed that therecess actually ends flush with the surface of the molding tool suchthat no edge, no bend and no slight undulation can be detected in theresulting component when the recess is filled with a placeholder. Sincethe trimming region does not remain on the component in any case, aslight shape deviation in this region is not critical.

The recess in the molding tool preferably extends outward from thetrimming region such that an overlap exists between the trimming regionand the recess. This makes it possible to remove the placeholder fromthe recess once the component has been laid, laminated and hardened.

As soon as the component is present in the molding tool in itsunfinished state—i.e., not yet trimmed to its final shape and alsoreferred to as “unfinished component” below—the placeholder can beremoved such that a cavity with an outward opening is created underneatha section of the trimming region. A lifting pad that consists of anelastic material and is expanded by being filled with compressed air oranother suitable medium can be inserted into this opening. In comparisonwith known wedge tools, this results in a very large-surface forceapplication such that no punctiform, one-sided load application, localbending or other load peaks are created. The force application is welldefined such that the limits with respect to the mechanical stability,e.g., a predetermined elastic line, are not exceeded due to the removalfrom the mold, particularly with thin-shell, large-surface components orcomponent sections. This results in a reduction of visible or invisibledamages to the composite fiber material such that elaborate additionalinspection steps for ensuring the integrity of, in particular,safety-relevant components can also be reduced. In this way, the costsdirectly associated with the manufacture of the component are lowered.

The final removal of a larger component can be ensured by subsequentlyinserting and inflating other lifting pads. Once the first lifting padhas been sufficiently inflated in the recess in order to slightly liftthe component out of the molding tool, another lifting pad can beinserted into the additional hollow space or intermediate space createdunderneath the component.

A maximum permissible elastic line of the component can be calculatedfrom the component dimensions. This elastic line is not exceeded due tocorresponding dimensions of the lifting pad. A system for manufacturingcomponents from composite fiber materials preferably may comprise anautomatic control of several lifting pads with a correspondinglyprogrammed computer unit or another electronic apparatus that controlsand monitors the component removal process.

Depending on the component geometry and the respective requirements, itwould be possible to use lifting pads with especially shaped geometries.This promotes the removal, in particular, of components with slightundercuts.

In component regions, in which an opening is produced or a geometricregion is removed in another manufacturing step, lifting pads oftemperature-resistant materials can already be used prior to thelamination of the component. In this case, it needs to be ensured thatthe molding tool is provided with a preinstalled connection for themedium to be supplied into the integrated lifting pad, and that thelifting pad is placed into the molding tool in such a way that no resincan pass between the molding tool and the lifting pad. Such preinstalledlifting pads that are distributed over the surface of the component tobe manufactured would make it possible to implement a fully automatedcomponent removal in a series production process. A central control onthe molding tool may control and inflate the lifting pads such that thecomponent is removed as carefully as possible.

In addition to open molding tool concepts with male or female moldingtools, the method according to the invention may also be used inconnection with closed tool concepts such as, e.g., in resin injectionmethods (“Resin Transfer-Molding,” RTM). In this case, the size of thelifting pads may be reduced such that they form knob-like lifting padsor lifting knobs. The component may be completely removed in a largelyautomated fashion, namely in the sense of a series production, bycontrolling several smaller integrated lifting knobs.

All in all, the method according to the invention for manufacturingcomponents from composite fiber materials provides a few advantages incomparison with known manufacturing methods, in which the components areconventionally removed in a manual fashion. For example, the path andthe force during the removal process may be controlled such thatunnecessary bending stress on the component may be prevented. Likewise,the risk of damaging the component during the removal is also reducedbecause a predefined maximum elastic line can be observed. In this way,the number of repairs required on components damaged during the removalprocess is reduced. Highly critical components such as, for example,solar cell panels of satellites can be carefully removed from the moldwith the proposed method, in particular, because no punctiform loadapplication occurs during the removal process. The surface load duringthe removal process can be adapted to special component geometries withthe concrete design of the lifting pad. An automation is possible inorder to save costs and time. If the component to be removed is veryrigid or very stiff, the method according to the invention also makes itpossible to apply significantly higher forces than currently knownmanual removal processes. If the lifting pads are connected in parallel,it is ultimately also possible to simultaneously lift several componentregions such that the local bending stresses are reduced.

Another aspect of the invention is a molding tool for manufacturingcomponents from composite fiber materials that comprises at least onerecess, into which a lifting pad can be inserted underneath thecomponent to be manufactured, within a trimming region. Yet anotheraspect is furthermore a use of such a molding tool, as well as anaircraft that comprises at least one component manufactured with amethod according to the invention.

It should be noted that characteristics and secondary effects of thepresent invention were described with reference to different embodimentsof the invention. Other characteristics, advantages and possibleapplications of the present invention result from the followingdescription of exemplary embodiments and the figures. In this respect,all described and/or graphically illustrated characteristics form theobject of the invention individually and in this combination, namelyregardless of their composition in the individual claims or theirreferences to other claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures, identical or similar objects are identified by the samereference symbols.

FIG. 1 a shows a schematic overview of a first variation of the methodaccording to the invention.

FIG. 1 b shows a schematic overview of a second variation of the methodaccording to the invention.

FIG. 2 illustrates a system, according to an embodiment of theinvention, for manufacturing a component from composite fiber materials.

FIG. 3 shows a schematic representation of a molding tool according tothe invention.

FIG. 4 shows an aircraft that comprises components manufactured with themethod according to the invention.

DETAILED DESCRIPTION

FIG. 1 a shows a first concept of the manufacturing method according tothe invention. In this exemplary embodiment, the method according to theinvention begins with the step of inserting 2 placeholders into thecorresponding recesses of the molding tool. Subsequently, the step ofproducing 4 the unfinished component is carried out. This step usuallyconsists of the individual processes laying, laminating and hardening,however, without claiming completeness and correctness of the sequencein this respect. The state of the art contains numerous differentprocedures for the production of an unfinished component from compositefiber materials such as, for example, the manual laying of fibers,manual laminating and subsequent hardening, as well as mechanized layingand resin injection methods.

The placeholders are removed 6 after the unfinished component has beenproduced. As already mentioned in the introduction to the description, arecess is situated in the molding tool underneath a trimming regionafter removing 6 the space holders. A lifting pad may be inserted 8 intothis recess and subsequently inflated 10. The inflation 10 shouldpreferably take place in a controlled fashion such that excessivebending loads on the component can be prevented. It is particularlypreferred to inflate 10 the lifting pads incrementally and tosubsequently insert 12 and likewise inflate 10 additional lifting padsin the thusly created intermediate spaces between the component and themolding tool. Due to this successive procedure, the component iscarefully removed from the molding tool.

A second exemplary embodiment of the method according to the inventionis illustrated in FIG. 1 b. The method according to Figure lb may becarried out alternatively or additionally to the method illustrated inFIG. 1 a. For example, larger components can be regionally manufacturedby using the method according to FIG. 1 a and in other regions byutilizing the method according to FIG. 1 b, e.g., if openings occur onlyin a region of the component.

In this case, lifting pads are already inserted 8 prior to theproduction of the unfinished component 4, for example, into regions ofthe molding tool, in which opening geometries or other geometryinterruptions are produced. This means that the lifting pad or thelifting pads lie in regions, in which no surface subsequently exists,such that possible bends, folds, undulations or the like are irrelevant.In this context, it is particularly important that the inserted liftingpads have a temperature resistance that makes it possible to introducethe lifting pad into a hardening device between the component and themolding tool. The hardening process may be carried out, for example, ata temperature that lies slightly below 200° C. such that the liftingpads for the method according to the invention, according to the secondexemplary embodiment need to have a correspondingly high temperatureresistance. It furthermore needs to be observed that the molding toolcomprises connections for a medium to be supplied to the lifting padsuch as, for example, compressed air connections.

After the production of the unfinished component 4, the lifting pads areinflated 10, wherein additional lifting pads are subsequently inserted12 into the intermediate spaces or hollow spaces created between thecomponent and the molding tool and subsequently also inflated 10. Inthis way, the successive lifting process by means of inflated liftingpads described with reference to FIG. 1 a is also realized in this case.

FIG. 2 shows one potential system according to the invention formanufacturing a component from composite fiber materials 14, whereinsaid system comprises a fluid source in the form of a compressor 16 thatis connected to lifting pads 20 via valves 18. Individual lifting padsor a combination of the lifting pads 20 shown can be selectivelyinflated by adjusting the flow resistance or the like of the individualvalves 18. The illustration in FIG. 2 should be interpreted in anexemplary fashion, wherein any number of lifting pads 20 or the liftingknobs mentioned in the introduction to the description may be utilized,namely in dependence on the size of the component to be manufactured,its complexity, undercuts or the like. In order to achieve the mosteffective component protection possible, it would be conceivable toutilize a computer unit 22 that monitors and controls the entirecomponent removal process. For example, the computer unit 22 may controlthe inflation of the individual lifting pads 20 independently of oneanother in order to automatically prevent the predetermined maximumelastic line of the component from being exceeded.

FIG. 3 shows an exemplary molding tool 24 that comprises, for example, arecess 26 for inserting a lifting pad 20. It should be clear to a personskilled in the art that the molding tool 24 may comprise a significantlylarger number of recesses 26. The region 28 illustrated with brokenlines in FIG. 3 represents the so-called trimming region, into which thecomponent being manufactured extends, wherein this trimming region istrimmed after the component has hardened in order to provide thecomponent with its final shape. It is obvious that a lifting pad can beinserted into the recess 26 when a component still lies flush on thesurface 30 of the molding tool 24. Part of the component can separatefrom the surface 30 of the molding tool 24 in the region of the recess26 when a lifting pad is inflated within the recess 26 such that otherlifting pads can be inserted between the surface 30 of the molding tool24 and the component.

FIG. 4 shows an examplary aircraft 32 with several components 34 thatwere manufactured with the method according to the invention, on themolding tool 24 according to the invention and by the use of a system 14according to the invention.

It should be noted that “comprising” does not exclude other elements orsteps, and that “a” or “an” does not exclude a plurality.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

REFERENCE SYMBOLS

-   2 Inserting placeholders-   4 Producing unfinished component-   6 Removing placeholders-   8 Inserting lifting pads-   10 Inflating lifting pads-   12 Subsequently inserting lifting pads-   14 System according to an embodiment of the invention-   16 Compressor-   18 Valve-   20 Lifting pad-   22 Computer unit-   24 Molding tool-   26 Recess-   28 Trimming region-   30 Surface of molding tool-   32 Aircraft-   34 Component

1. A molding tool for producing a component from composite fibermaterials according to a method comprising inserting at least oneplaceholder for a lifting pad into at least one respective recesse in amolding tool, producing an unfinished component, removing theplaceholder, inserting at least one lifting pad into the at least onerecess and removing the unfinished component from the mold by inflatingthe at least one lifting pad, the molding tool comprising a recess intowhich the at least one lifting pad underneath a region of the componentto be manufactured is insertable.
 2. The molding tool of claim 1,wherein the recess is arranged in a trimming region of the component tobe manufactured.
 3. The molding tool of claim 2, further comprising: atleast one fluid source for inflating the at least one lifting pad; atleast one valve for the at least one lifting pad; and at least onecomputer unit for controlling the at least one valve.
 4. A system formanufacturing components from composite fiber materials according toclaim 1, further comprising: at least one fluid source for inflating theat least one lifting pad; at least one valve for the at least onelifting pad; and at least one computer unit for controlling the at leastone valve.
 5. The system of claim 4, wherein the computer unit isadapted for controlling the at least one lifting pad in such a way thata predetermined maximum elastic line of the unfinished component is notexceeded.
 6. An aircraft with at least one component made of a compositefiber material that was manufactured in accordance with a methodcomprising inserting at least one placeholder for a lifting pad into atleast one respective recesse in a molding tool, producing an unfinishedcomponent, removing the placeholder, inserting at least one lifting padinto the at least one recess and removing the unfinished component fromthe mold by inflating the at least one lifting pad.